1. Field of the Invention
This invention pertains to technologies employed in tracking and control of contents of containers on assembly lines, and during warehouse handling and shipment, and particularly to technologies employing Radio Frequency Identification (“RFID”) tags.
2. Background of the Invention
Radio Frequency Identification (“RFID”) systems are becoming more and more popular for monitoring and tracking objects, animals, and sometimes even people. For example, RFID systems are used in stores for monitoring and tracking items for sale, in libraries for tracking books, in warehouses for tracking goods, on farms for monitoring cattle or livestock herds, and in roadway tolling systems for tracking passing vehicles. As the costs of manufacturing RFID components continue to decrease and the technology associated with RFID components improves, people are finding more and more applications in which to employ RFID technologies. Additionally, people are continually improving the technology and finding ways to circumvent performance limitations associated with RFID systems.
RFID systems typically consist of radio frequency (“RF”) tags, RF tag readers, and some type of computer running software to process information obtained from tag reads, or interrogations. The tags typically respond to an RF query, or interrogation, signal broadcast initiated by the tag reader. The tags usually send out pre-configured information, such as serial numbers or other data stored within differing types of memory devices coupled to the tags. RFID tags and tag readers usually operate without any line-of-sight requirements. The tags and readers can usually also receive and transmit signals through nonconductive materials.
Turning to FIG. 5, RFID-based systems various embodiments may use wireless radio signals (53) to identify objects. In one of its most elemental forms an RFID system (50) may comprise two components, an RFID tag (51) and an RFID reader (52). RFID tags for various embodiments, which may be referred to as RFID cards or RFID transponders, may exist in many shapes and sizes. Generally, they may contain one or more coils to serve as an antenna (54), and a radio transceiver (55) contained on a silicon microchip. The coiled antenna may also be used to induce power from the reader (52) to the tag so that the tag is not required to have its own power source. The microchip may also store information (56), such as a unique identification number for identifying the object to which the tag is attached. Some RFID tags may allow a reader to update or change the information stored in the tag.
RFID tags in various embodiments may be classified as passive or active. Passive tags may generally not broadcast any information stored within the tag until activated by an RFID reader. Active tags, on the other hand, may constantly broadcast identification or information stored on the microchip. These active tags may contain batteries (57). The batteries may provide additional power for transmitting from the transceiver and operating the microchip. The batteries may allow the tags to send their data greater distances than passive tags.
RFID readers may have the same basic components as RFID tags, including an antenna (54′) and reader electronics including an RF transceiver (55′) and a processor-based computer circuit (58). The reader may also serve as a programmer for tags which can be re-programmed, or tags which are being initially programmed. Many readers, and especially those involved in inventory control or loss prevention, also interconnect to a network (59), such as a local area network or a wireless LAN, in order to communicate with inventory systems, point-of-sale terminals, etc.
To illustrate a basic RFID inventory control function, FIG. 6 shows a product package (60), such as a carton, box, blister pack, or bottle, in two positions (a) and (b) relative to a reader, such as a point-of-sale system (63) or a hand-held reader (52′). The product is configured with an RFID tag (51), which is often located within the package just behind a barcode or Universal Price Code (“UPC”) printed on the outside of the package (60). Some RFID devices, however, are more cleverly hidden within the product to prevent tampering.
As the package (60) is moved (62) within RF range (53, 53′) of a reader, the reader transmits a code which activates the tag (51), and the tag responds by transmitting one or more codes back to the reader. In current standardized technologies, frequencies used fall into low frequency (“LF”) and high-frequency (“HF”) ranges, 30 KHz to 500 KHz, and 850 MHz to 950 MHz or 2.4 GHz to 2.5 GHz, respectively. LF systems have a reader range of approximately 6 feet, while HF systems may provide a reader range of 90 feet or more. One organization, EPCglobal Incorp., provides open industry standards for such RFID technologies to insure compatibility between tags and readers. These standards include formats of the data and codes used for activation, programming, and identification. Identification codes usually include identifiers. For example, EPC Tag Data Standard Version 1.1 rev 1.27 specifies encoding schemes for a serialized version of the EAN.UCC Global Trade Item Number (“GTIN”)™, the EAN.UCC Serial Shipping Container Code (“SSCC”)™, the EAN.UCC Global Location Number (“GLN”)™, the EAN.UCC Global Returnable Asset Identifier (“GRAI”)™, the EAN.UCC Global Individual Asset Identifier (“GIAI”)™, and a General Identifier (“GID”)™. It is suffice to say, since these standards are well known and open to the industry, that this information provides a method to identify the tagged product by product maker/manufacturer, product model, and serial number, which we will refer to throughout the rest of this disclosure as make/model/serial-number (“MMSN”). Other standards may be employed, of course, and especially proprietary encoding and transmission schemes.
Now consider a situation of tracking multiple tagged products as they are packaged or unpackaged in and out of a shipping container (70), as shown in FIG. 7. This illustration is greatly simplified showing just two tagged products (71, 73), but in reality, a shipping container may hold many tens, hundreds, or even thousands of individually tagged products. This products can be placed into (72) the aggregating container (70), or removed from the aggregating container (70). Placing products into a container happens often during order fulfillment, when the tagged items may or many not be of identical make and model (“MM”). Filling or “packing” a container may just as well contain many items of the same MM, but each having a different serial number (“SN”), such as packing performed on production lines. Production and shipping lines may also fill containers with tagged products of different MM when packaging kits, as well.
Using RFID to monitor the inventory or contents of the container has proven difficult, in part due to the clustering of many tagged products simultaneously within range of a reader, and in part due to physical restrictions of placement of the reader with respect to paths of ingress and egress of tagged products to and from the container. For the remainder of this disclosure, we will refer to containers as physically enveloping structures, such as boxes, cartons, or trays, as well as platforms on which groups of tagged products can be packed, such as pallets.
For example, one solution from ODIN Technologies, called the ODIN Smart Container, The ODIN Smart Container, attaches an RFID reader and an active RFID tag to the container door. As items are added and removed from the container, the RFID reader tracks this information and updates its active tag which provides a dynamically maintained list of the inventory of the container. Apparently, the positioning of the reader at the door is key to determining when a tagged item is arriving or leaving the controlled space within the container. As items move through the door (e.g. within range of the RFID reader), they are first checked to see if they are on the current inventory or container manifest, and if they are not, they are added to the manifest, otherwise, if they are they are removed from the manifest. This method is sufficient for very large containers, such as Supply Line Application containers, where the items will be out of range for the RFID reader once they've passed through the door of the container. But, on much smaller containers, such as those less than 6 feet in any dimension, including many Assembly Line Application containers such as human-liftable cardboard boxes, the contained tagged products would always be in range of the reader. This renders the inventory monitoring method ineffective.
Another example is the SAVI Sentinel product, which is a battery-powered RFID reader that clamps to a standard intermodal shipping container, such as containers used for shipboard and rail transportation. The Sentinel acts as a sensor that can detect if the container has been opened, and monitors other sensors that report on the conditions and integrity of goods in the container. It also provides two-way wireless communications within a supply chain network to enable real-time auditing. It does not provide any tracking of the inventory within the monitored container, however,
It is in this situation of a container which is relatively small compared to the range of the RFID system which presents a problem unsolved in the art. For example (80), in FIG. 8, a conveyor belt (81) of an assembly line, packing line, or order fulfillment line, is shown. A packed container (70) having a plurality of tagged products within it (not shown) move into range r of an RFID reader (52). If the range r is equal to or greater than the dimensions d and d′ of the container (70), then many tagged products will respond nearly simultaneously as they enter the range of the reader. The faster the conveyor travel, the more prominent this problem becomes.
Therefore, there is a need in the art for a system and method to effectively monitor and track the inventory of container contents in which a plurality of RFID tagged items are stored wherein the container size is approximately equal to or smaller than the effective range of the RFID technology employed.